Among patients with opioid use disorder (OUD), 90% report lifetime trauma exposure and 33% meet criteria for posttraumatic stress disorder (PTSD). The co-occurrence of OUD and PTSD is associated with more severe mental health symptoms and worse opioid agonist treatment (OAT) outcomes relative to either diagnosis alone. Prolonged exposure therapy (PET) is an efficacious manualized cognitive-behavioral treatment for reducing PTSD severity. Although preliminary findings indicate that PET may reduce PTSD symptom severity among patients receiving treatment for concomitant OUD, it is unclear to what extent observed improvements were a function of PET versus the psychopharmacological effects of OAT itself. Therefore, the question of whether OAT alone may attenuate PTSD symptomatology in the absence of intensive cognitive-behavioral therapy remains unanswered and is important given the prevalence and deleterious effects of PTSD among OAT patients, as well as the ever-present constraints on mental health resources in SUD treatment settings.